Method and system for subscription television billing and access

ABSTRACT

A subscription television system and method in which billing information regarding programs actually viewed by a subscriber of the system is accumulated over non-dedicated telephone lines. A scrambled television program signal containing a block of television program material, a program identification code unique to the block of program material, and a program category code, is broadcast. The codes are preferably included in the vertical retrace interval of the video portion of the program signal and the transmitted program signal is selectively received at a subscriber station and selectively unscrambled to permit viewing of the block of program material being transmitted in response to subscriber action indicating acceptance for viewing of the block of program material. The received program category code is compared with a locally generated category code to determine whether the program is acceptable for viewing. The program identification code is detected and stored for subsequent transmission in response to the subscriber action indicating acceptance for viewing of the received block of program material. 
     The program identification code stored at the subscriber station is selectively accessed from a remote location over telephone lines on other than a real time basis (e.g., a periodic basis) to thereby provide billing information at the remote location as to programs actually viewed by the subscriber. The subscriber can thus be billed monthly or on some desired periodic basis for programs actually viewed during the preceding period. The billing period can be varied from the remote location to provide a means to control the number of programs which a subscriber can receive.

This is a continuation of application Ser. No. 365,498, filed Apr. 5,1982, now abandoned, which is a continuation of application Ser. No.190,657, filed Sept. 25, 1980, now abandoned, which is a division ofapplication Ser. No. 920,846, filed June 30, 1978, now U.S. Pat. No.4,225,884, which is a continuation-in-part Ser. No. 768,404 filed Feb.14, 1977, now U.S. Pat. No. 4,163,254.

BACKGROUND OF THE INVENTION

The present invention relates to subscription television and moreparticularly to a method and system for obtaining billing informationregarding programs viewed by a subscriber of a subscription televisionsystem.

Since the advent of subscription or pay television, numerous techniqueshave been devised to bill the subscribers for the service provided. Ithas been suggested that the subscriber pay for subscription televisionservices on a fixed charge basis, a uniform cost per unit use basis, oron a per program charge basis. More recent systems have adopted the perprogram basis for billing.

It will be appreciated that a fixed charge or uniform charge per unitbasis of billing presents the least problems with regard to recordingand calculating billing charges. With a fixed charge system as is usedwith most cable television or CATV systems, the station operator merelybills the subscriber a fixed amount on a monthly basis.

The uniform per unit use billing involves somewhat more complexprocedures since actual viewing time must be recorded and somehow madeavailable to the operator for billing purposes. Moreover, the viewingtime must be registered in conjunction with the identity of eachsubscriber so that an individual subscriber can be billed for hisviewing time.

The most complex billing system and yet the most desirable from thestandpoint of the subscriber is billing on the basis of actual programsviewed with different charges for different programs. In such a system,the billing entity must know both the identity of the subscriber and theidentity of the programs viewed during a billing period.

Several billing systems have been developed in order to chargesubscribers to a pay television system on the basis of programs actuallyviewed. Typical of these types of systems are the coinbox systems thatare exemplified by U.S. Pat. No. 3,021,383. In such a system, thesubscriber must deposit a certain amount of money in a coinbox attachedto the receiver in order to view a particular program. Differentprograms may be assigned different charges so that, for example, aparticular movie may cost less to view than a sporting event. With sucha system, payment for the program enables the viewing of a program andpayment is thus assured. However, the billing entity (the systemoperator) must collect the money from the coinboxes on a periodic basis,requiring considerable manpower and also requiring access to thesubscriber's home.

Another approach to billing on a per program basis requires thesubscriber to place a telephone call to some central location andrequest the receipt of a particular program. The calling subscriber'sequipment is then enabled and charges for the program can be recordedand billed to the calling subscriber. It will be appreciated that such asystem may encounter difficulties in large service areas with a largenumber of subscribers. In addition, the subscriber's telephone must beutilized frequently for this purpose.

Other approaches to the billing problem in pay TV systems include theone of cards or paper tapes that are used at the subscriber location torecord viewing information. In a particular system, a card is mailed tothe subscriber and is required for operation of the subscriber'sreceiver. The card is punched or otherwise imprinted at the subscriberlocation to record program charges and must be mailed or otherwisetransmitted to the system operator so that charges may be assessed.Typical of these types of systems are those shown in U.S. Pat. Nos.3,470,309, 3,475,547 and 3,531,583.

Another type of billing system may be characterized as a real timemetering or interrogating system such as that shown in U.S. Pat. Nos.3,396,232, 3,716,654 and 3,733,430. These systems typically interrogatethe receivers or otherwise monitor the status of the receivers on aprogram by program basis (e.g., through the use of special transducers)to determine if the subscriber is watching a particular program. Thisinformation can then be used for billing purposes as well as audiencesurvey purposes and the like.

It can be seen that the foregoing systems suffer from numerousdeficiencies including system complexity, enormous time consumption,reliance on subscriber action to receive billing information, and thelike. It is accordingly an object of the present invention to obviatethe foregoing and other deficiencies of the prior art pay televisionsystem billing procedures through the use of a novel method and systemfor billing on a per program basis with a minimum of complex equipmentand a minimum of human intervention.

It is another object of the present invention to provide a novel methodand system for obtaining billing information regarding programs actuallyviewed by a subscriber of a pay television system wherein programidentification data is recorded and is accessed on a periodic basis froma central location, thus, eliminating the need for the gathering of theinformation through the intervention of the system subscriber.

It is yet another object of the present invention to provide a novelmethod and system for obtaining billing information regarding programsactually viewed by a pay television system subscriber which utilizes aminimum of complex equipment and makes use of existing equipment at thesubscriber location including a telephone at the location.

It is a further object of the present invention to provide a novelsubscriber television system and method in which scramble and programcodes are received in the program video signal and are used inconjunction with a telephone access unit to unscramble the receivedprogram signal and record program viewing under the control of a centralstation linked to the access unit over non-dedicated telephone lines.

It is another object of the present invention to provide a novelsubscriber television system and method in which the subscriber has thecapability to select a program for viewing from among a number ofdifferent available programs and selectively prevent the viewing ofothers of the available programs.

It is yet a further object of the present invention to provide a novelsubscriber television system and method in which the length of thebilling period can be varied to provide flexibility in the control ofprograms available to the subscriber.

These and other objects and advantages of the present invention willbecome apparent to one skilled in the art to which the inventionpertains from the following detailed description when read inconjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a subscription or paytelevision system in accordance with the present invention;

FIG. 2 is a signal diagram illustrating an exemplary form of the videoportion of the program signal with scramble and program ID codes asutilized in the system of FIG. 1;

FIG. 3 is a functional block diagram illustrating the centraltransmitting station of FIG. 1 in greater detail;

FIG. 4 is a functional block diagram illustrating the subscriber stationequipment of FIG. 1 in greater detail;

FIG. 5 is a functional block diagram illustrating an access unit with asettable clock for providing variable length billing periods; and

FIG. 6 is a block diagram illustrating a category selection device whichcan be included with the subscriber station equipment.

DETAILED DESCRIPTION

Referring now to FIG. 1, the system according to the present inventiongenerally comprises central station equipment 10 which supplies programsignals in a scrambled form to subscriber station equipment 12 at eachof the subscriber stations. As will be described hereinafter in greaterdetail, the scrambled program signal includes scrambled audio and videosignals as well as various synchronizing signals and codes. Thescrambled program signal SPROG is supplied to the subscribers either byconventional broadcast or cable techniques.

The audio and video signals from a conventional source such astelevision camera equipment are applied to a program signal scrambler 14to produce respective scrambled audio and video signals SAUD and SVID.In addition, the program signal scrambler 14 provides a transmittedscramble code TSC for transmission with the scrambled program audio andvideo signals. The SAUD, SVID and TSC signals from the scrambler 14 areprovided to a suitable conventional transmitter 16 for production of ascrambled program signal that includes the code signals and fortransmission to subscriber stations.

A program ID code unit 18 synchronized with the scrambled video signaland scramble code provides a program code TPC for transmission with theprogram signals. This program ID code TPC is combined with the scrambledprogram video and the scrambled code for transmission to the subscriberas is described hereinafter in greater detail. In addition, the centralstation equipment 10 may include a billing data gathering computer 20.It should however be understood that the billing data gathering computer20 may be located at any convenient central location and need not belocated at the transmitting site.

The scrambled program signal SPROG from the central station equipment 10is received by a program signal receiver 22 at the subscriber stationand the received signal is supplied both to a program signal unscrambler24 and to a control and storage unit 26. The program signal unscrambler24 operates in response to control signals from the control and storageunit 26 to unscramble the incoming program signal and provideunscrambled audio and video signals UAUD and UVID to a conventionalmodulator 28. The modulator 28 modulates a carrier signal of anappropriate carrier frequency with the unscrambled audio and videosignals and supplies the unscrambled program signal in the form of amodulated carrier wave to the television antenna terminals for use bythe subscriber's television set in a conventional manner.

A subscriber control unit 30 provides subscriber control of programviewing. The subscriber control unit 30 may, for example, include one ormore subscriber manipulated controls which permit the subscriber toselectively tune a conventional tuner in the program signal receiver 22in order to select a desired program as well as to provide appropriatesignals to the control and storage unit 26 indicating that thesubscriber has selected a program for viewing and has thus assumed theobligation to pay that program.

The control and storage unit 26 detects code signals in the incomingscrambled program signal for unscrambling and billing purposes. In thisrespect, the transmitted scrambled code TSC is detected by the controland storage unit 26 and compared to a received scramble code RSCsupplied to the control and storage unit through an access unit 32 andstored in the control and storage unit. The control and storage unit 26also detects the transmitted program code TPC in the incoming programsignal and stores the program code of a particular program being viewed.The stored program code SPC is then supplied on command to the accessunit 32. As illustrated, the access unit 32 is connected to telephonelines which are in turn connectable through conventional telephoneswitching equipment to the telephone lines leading to the billing datagathering computer 20.

In operation, the audio and video program signals are supplied to theprogram signal scrambler 14 and are scrambled in any suitableconventional manner. For example, these signals may be scrambled inaccordance with the techniques described in U.S. Pat. No. 3,824,332through selective inversion of portions of the video signal. Thescramble code TSC may be inserted into the video signal in order topermit unscrambling of the program signals at the subscriber station asis set forth in U.S. Pat. No. 3,824,332.

In addition, each program that is transmitted in a scrambled form may beidentified by placing a program code TPC in the video signal during thevertical retrace interval of the signal or at any other convenientlocation. In this connection, the program code and scramble code may becombined with the program video at the appropriate locations bysynchronizing the generation of these codes with the video synchronizingsignals in any known manner such as that shown in the referenced U.S.Pat. No. 3,824,332.

The program signal transmitter 16 combines the video and code signalsand transmits this combined signal together with the audio signal at anappropriate carrier frequency. The resultant video portion of theprogram signal may thus take the form illustrated in FIG. 2. Forexample, as is illustrated in FIG. 2, the successive horizontal lines ofthe video signal are conventionally separated by horizontalsynchronization pulses and each frame of video signals is separated by avertical retrace interval or vertical synchronization signal. During thevertical retrace interval, various equalizing and synchronization pulsesare provided and it is in this interval that the scrambled and programID codes are preferably combined with the transmitted program signal.These codes are preferably encoded in a digital form as illustrated inFIG. 2 although it should be understood that any well known codingtechnique such as the tone burst technique described in U.S. Pat. No.3,824,332 may be utilized.

With continued reference to FIGS. 1 and 2, the transmitted program videosignal is thus in the form of a scrambled signal (e.g., with selectedframes of video information inverted) with codes inserted at appropriatelocations to identify the program being transmitted and to indicate tothe subscriber equipment the state of the subsequent video signal (i.e.,inverted or non-inverted). The program signal receiver 22 selects aparticular carrier frequency through the use of a conventional tuner anddemodulates the incoming program signal to recover the audio, video andcode signals.

The recovered scrambled program signal is supplied to the program signalunscrambler 24 and to the control and storage unit 26 for unscramblingand detection of the codes contained in the video portion of the programsignal. The scramble codes detected in the program signal are used togenerate the control signals that control the unscrambling of theprogram signal by the unscrambler 24. The program code in the incomingvideo signal is stored in a storage unit that may be selectivelyaccessed by an access unit 32. The access unit 32 may be, for example,of the type disclosed in copending U.S. patent applications Ser. No.683,161 filed May 4, 1976 and Ser. No. 701,033 filed June 29, 1976, bothby Robert S. Block and John R. Martin.

It will be appreciated that the invention provides a relatively simplemanner of subscriber billing that allows for the identification ofprograms actually viewed and the rapid gathering of this information ona periodic basis long after a program has been viewed. Each subscriberstation is selectively accessed so that program viewing information inassociation with subscriber identification information is available at acentral location for billing purposes. Moreover, the billing gatheringcomputer 20 has complete control over the subscriber station equipment12 in the sense that it can deny new scrambled codes to the subscriberstation equipment on a selective basis if that particular subscriber hasnot paid his bill or for other relevant reasons.

To facilitate an understanding of the present invention, the centralstation equipment 10 and the subscriber equipment 12 are illustrated ingreater detail in FIGS. 3 and 4, respectively.

Referring to FIG. 3, the central station equipment receives theunscrambled program signal UPROG including the audio and video portions.The audio portion is applied to a program audio scrambler 42 and to avideo sync detector 44. The video sync detector 44 detects anappropriate synchronization pulse in the video signal, e.g., thevertical sync pulses, and supplies the sync pulse to a scramble codegenerator 46 and to the program ID code unit 18. The scramble codegenerator 46 supplies a video scramble control signal VCS to the programvideo scrambler 42 and an audio scramble control signal ACS to theprogram audio scrambler 40. The program signal is thus scrambled toproduce a scrambled audio signal SAUD and a scrambled video signal SVIDin a conventional manner. In addition, the scramble code TSC isgenerated by the scramble code generator 46 so as to identify the mannerin which the program signal has been scrambled.

As was previously mentioned, the program ID code unit 18 receives thesync signal from the video sync detector 44 and generates the programcode signal TPC. In this connection, a program ID code selector 48 maybe provided to control the generation of a particular program code by aprogram ID code generator 50. Thus, the station operator can select aparticular code for a particular program in this manner.

The scrambled audio and video signals together with the scrambled codeand program code are supplied to the scrambled program signaltransmitter 16 comprising a signal combiner 52 and conventionalmodulators and transmitters 54. The signal combiner 52 receives thescrambled video, scramble code and program code signals and combinesthese signals in a conventional manner to produce a signal such as thatillustrated in FIG. 2. This combined signal is then applied to themodulators and transmitters 54 together with the scrambled audio signalfor modulation of these signals onto a suitable carrier wave fortransmission.

It will thus be appreciated from the diagram of FIG. 3 that the videosync detector 44 detects the appropriate synchronization pulse in thevideo signal in order to trigger the scramble code generator 46 and theprogram ID code generator 50 at appropriate times. For example, thevideo sync detector 44 preferably detects the vertical sync pulse duringthe vertical retrace interval of the video signal. This vertical syncpulse triggers the scramble code generator 46 in order to cause theprogram video signal to be inverted or passed uninverted at anappropriate time. In addition, the detected sync signal triggers thescramble code generator and the program ID code generator in order tosynchronize the generation of the scramble code and program code signalsTSC and TPC with the occurrence of the vertical retrace interval. Theaudio scramble control signal ACS generated by the scramble codegenerator 46 may be any suitable control signal and need not besynchronized to the video synchronization pulses.

The signal combiner 52 conventionally combines the video and codesignals and the modulators and transmitters 54 provide appropriatemodulated signals for either broadcast or cable transmission.

Referring now to FIG. 4, the program signal receiver 32 at thesubscriber station may include a conventional tuner 56 and aconventional demodulator 58. The scrambled program signal is supplied tothe tuner 56 and to the demodulator 58 for recovery of the scrambledaudio and scrambled video signals. The scrambled video signal, ofcourse, contains the program and scramble codes in addition to videoinformation. Control of the tuner 56 and thus selection of a particularcarrier frequency may be accomplished in a conventional manner by acontrol knob on the subscriber control unit 30. The control unit 30 maytherefore be referred to as a program select and accept control sincethis control also may provide for the application of an accept signalACC to the control and storage unit 26 as an indication that thesubscriber has assumed the obligation to pay for a particular program towhich the equipment is tuned.

The scrambled audio signal is supplied to a program audio unscrambler 60and the scrambled video signal is supplied both to a program videounscrambler 62 and to a code detector 64 in the control and storage unit26. The code detector 64, when enabled by the accept signal ACC, detectsthe received scramble code RSC and the received program code in thevideo signal. The received scrambled code is supplied to a scramble codecomparator 66 and the received program code is supplied to aconventional signal storage device 68 for storage and later recall bythe access unit 32.

The scramble code comparator 66 receives a stored scramble code signalSSC from the signal storage device 68 and generates the video and audiounscramble control signals VCS' and ACS', respectively. These twosignals are supplied to the respective program video unscrambler 62 andthe program audio unscrambler 60 in order to reconstitute the scrambledvideo and audio signals to their original form prior to scrambling bythe program signal scrambler 14 at the central station equipment. Thisunscrambling process may take the form, for example of that illustratedand described in previously referenced U.S. Pat. No. 3,824,332. Thus,for example, when the received scramble code RSC is compared to thestored scramble code SSC and is identified as an invert signal, the VCS'signal causes the program video unscrambler 62 to invert the subsequentframe of video signals. Similarly, when the received scramble code iscompared with the stored scramble code and is identified as a non-invertsignal, the video signal is passed by the program video unscrambler 62in an uninverted form.

The access unit 32 is connected to the telephone lines as was previouslydescribed and provides access between the billing data gatheringcomputer 20 and the signal storage device 68. The subscriber stationequipment may be accessed in any one of the various ways disclosed inthe previously referenced copending patent applications of Block andMartin such as through the timed placement of a call from the accessunit 32 to the computer 20 (e.g., the placement of a call on a monthlybasis). Similarly, when the signal storage device 68 is full and canstore no more program codes, the access unit 32 may place a call to thedata gathering computer 20 to transfer billing information thereto.

In this connection, the computer 20 and access unit 32 may be connectedover the telephone lines through conventional telephone switchingequipment as commanded either from the access unit 32 or from thecomputer 20. After the connection is effected between the computer 20and the access unit 32, various data may be transmitted over thetelephone lines.

The computer 20 may, for example, initially command the access unit 32to transmit the stored program code signals SPC from the signal storagedevice 68 to the computer 20. This may be accomplished in any suitablemanner as, for example, by sending a code to the access unit 32 andgenerating an interrogate or read signal INT which causes the signalstorage device 68 to supply the stored program codes SPC to thetelephone lines and therefore to the computer 20. Similarly, thecomputer 20 may transmit a code to the access unit 32 commanding it togenerate a strobe or write signal STR in order to transmit new scramblecodes RSC through the access unit to the signal storage device 68.During normal operation, then, the signal storage devise may be suppliedwith scramble codes for one month's programs and at the end of thatmonth new scramble codes may be supplied for the next month'sprogramming. At the same time, the program codes stored in the signalstorage device 68 may be accessed and transferred to the computer 20 sothat the subscriber may be billed for actual programs viewed during thepreceding month at various rates for various programs.

An embodiment of an access unit which provides for variable control ofthe billing period is illustrated in FIG. 5. The access unit 32 includesan UP-DOWN counter 70 which comprises a settable clock and provides asignal to indicate when the computer 20 should be called to perform abilling operation. The DOWN or alternatively the PRESET input terminalof the counter 70 is connected to a discriminator 72 which transmits abilling period length signal BPL received from the computer over thetelephone lines. The discriminator 72 can also transmit other signalsreceived over the telephone lines to other circuitry in the access unit32 and to the signal storage device 68 (e.g., the INT and STR signals).The billing period length signal BPL reduces the count in the counter bya predetermined amount or alternatively presets the counter to apredetermined count corresponding to the length of the desired billingperiod, e.g., one month.

The UP input terminal of the counter 70 is connected to a clock 74. Itwill be obvious that the frequency of the output signal of the clock 74will be determinative of the amount the count in the counter 70 isreduced by the signal BPL to obtain the desired billing period length.

An output terminal of the counter 70, e.g., the zero count outputsignal, is connected with an automatic telephone dialing unit 76. Aftera period of time determined by the billing period length signal BPL, thecount in the counter 70 will reach a predetermined value such as zeroand a billing time signal BTS will be transmitted to the dialing unit76. This enables the dialing unit 76 and causes it to place a call tothe computer 20 to provide a connection between the computer 20 and theaccess unit 32.

Once the connection between the access unit 32 and the computer 20 ismade, the previously described procedures associated with the billingoperation are performed. In addition, a new billing period length signalBPL is transmitted to the access unit 32 to preset the counter 70 to apredetermined value, to establish a new billing period, and remove thebilling time signal BTS. A signal lamp 77 can be connected to thecounter 70 to indicate when a billing operation is taking place.

An output terminal of the counter 70 can be connected to the codedetector 64 to provide an inhibit signal INHIB which prevents operationof the code detector after the termination of one billing period andprior to the beginning of the next succeeding billing period. Theinhibit signal may also be connected to the clock 74 to inhibit theclock and so that the inhibit signal is maintained until the counter isagain preset by the BPL signal.

Prior to generation of the billing time signal BTS, the inhibit signalINHIB is in a low state. This signal is inverted by an inverter 78 andenables an AND gate 80. A second input terminal of the AND gate 80 isconnected with an output terminal of the program select and accesscontrol 30 to receive the accept signal ACC. As long as an inhibitsignal is not generated, the accept signal is transmitted to the codedetector 64 by means of the AND gate 80.

If, however, the count in counter 70 has reached the inhibit value andthe inhibit signal INHIB is generated, the AND gate 80 will be disabled.The subscriber will not be able to actuate the code detector 64 toreceive a broadcast program until the counter 70 is reset by a billingperiod length signal BPL from the computer. A signal lamp 82 can beconnected to the output terminal to indicate that the system is in theinhibit mode.

The billing period length signal BPL can be varied by the computer toprovide a means of flexible control over the amount of program materiala subscriber will be able to receive and view. For example, the billingperiod length signal will normally set the length of the billing periodto be one month, i.e., the counter will reach the predetermined countthat generates the INHIBIT and BTS signals around 30 days after the BPLsignal presets the counter. At the end of the onemonth billing period,the computer is dialed by means of the automatic dialing unit 76 inresponse to the BTS signal and the computer is fed the billinginformation stored in the signal storage device 68.

The computer checks to determine whether the subscriber's bill for theprevious billing period has been paid. If it has, the computer sends outa billing length signal which resets the counter 70 for anotherone-month period and supplies the new scramble codes for the nextmonth's programming.

If, however, the subscriber's previous bill has not been paid, thecomputer 20 will send out a billing period length signal BPL whichresets the counter 70 for a one-week billing period, for example. In theexample above, only the scramble codes for the week's worth ofprogramming will be transmitted to the access unit 32.

After one week in the above example, the billing time signal BTS will begenerated and the computer 20 will be connected to the access unit 32.The computer will again check to determine whether the bill has beenpaid. If it has, a billing period length signal will be transmitted bythe computer to reset the billing period to terminate at the end of theone month period of which one week has elapsed. The remainder of thescramble codes for the month's programming will also be supplied.

If the subscriber's bill has not yet been paid, a new length signal(which may be zero) will be furnished by the computer. The inhibitsignal INHIB will prevent the subscriber from viewing any of thetelevised programs until the bill has been paid, or the decoder will begiven no enable codes and therefore is inhibited from decoding. Thesignal lamp 82 indicates that the bill must be paid before furtheraccess to the broadcast programs can be achieved.

The inhibit signal INHIB can be generated simultaneously with generationof the billing time signal BTS to prevent access to broadcast programsduring billing operations and until the counter 70 is reset.Alternatively, the inhibit signal can be generated a short time afterthe billing time signal, e.g., one minute, to allow normal billingoperations and reset to occur without interference with program accesswhen bills have been paid promptly.

As a further feature of the present invention, a plurality of differentprograms which are categorized according to content can be selectivelyprovided to the subscriber. One embodiment for providing such acapability is illustrated in FIG. 6.

The program access and control 30 includes a switch 84 or similar suchdevice which allows the subscriber to indicate that a particularbroadcast program is desired by generating the accept signal ACC. Inaddition, the control unit 30 includes a category selector knob 86. Theselector knob 86 is preferably a key controlled switch which can belocked and turned to a desired category of programming only by means ofa special key. The selector knob 86 includes a pointed indicator 88which can be turned to a number of different category positions such asA, B, C, and X.

The different categories such as A, B, C and X can representclassification of the broadcast programs based upon subject mattercontent of the programs. For example, the classification breakdown canbe as follows:

A: Suitable for viewing by the public in general;

B: Subject matter requiring patental guidance;

C: Restricted subject matter; and

X: X-rated material.

Alternatively, a category S can be set up for special interest groups,such as doctors, lawyers, etc. In such a case, the classifications couldbe as follows:

A: General;

B: Parental Guidance;

C: X-rated; and

S: Special interest.

Furthermore, the logic circuitry associated with the selector knob isdesigned so that subscribers belonging to one special interest groupwill not receive those intended for a different group, i.e., lawyerswill not receive educational programs for doctors.

The selector knob 86 can be connected to a category code generator 90.The code generator 90 is responsive to the position of the selector knob86 and generates a signal containing the code or codes identifying thecategory or categories which have been chosen as acceptable for viewing.For example, if the selector knob is set to the "A" position, a codeword will be generated indicating that only A category programs are tobe unscrambled. If the "B" position is selected, a code or words will begenerated indicating that A or B category programs can be unscrambled.The "C" position will cause generation of a code word or words toindicate that A, B or C category programs can be unscrambled, and "X"will indicate that any of the four categories of programs areacceptable.

The output signal of the category code generator 90 is fed to acomparator 92. The comparator 92 also receives a signal identifying thecategory in which the received program is classified. This coded signalcan form part of the program code signal TPC. For example, if theprogram code signal is a digital signal, the category code may becontained in the first three bits of the program code signal.Alternatively, different groups of program identification numbers can beassigned to programs of different categories. For example, programsnumbered 1-200 will be "A" category programs, programs numbered 201-500will be "B" category programs, etc. Thus, no additional data will berequired to be braodcast with the program I.D. signal and the "A"position of the switch 86 will allow decoding (unscrambling) of allprograms numbered 200 or below, the "B" position all programs numbered500 or below, etc.

The category signal present in the incoming broadcast signal is detectedby a detector 94 and fed as an input signal to the comparator 92. Thecomparator compares the two input signals and if they correspond, i.e.,the category of the broadcast signal is acceptable for viewing, anenabling signal is produced at the output terminal. The enabling signalenables an AND gate 96, which transmits the accept signal ACC to thecode detector 64.

The category selection feature permits selective control by thesubscriber of the programs which can be viewed. Furthermore, the keylock selector knob allows parents to prevent unauthorized viewing bychildren of programs having sensitive subject matter.

From the foregoing description, it will be made clear that the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than the foregoing description,and all changes which come within the meaning and range of equivalencyof the claims are therefore intended to be embraced therein.

What is claimed is:
 1. In a television system in which subscriptionprogram signals containing subscription program material are transmittedto subscribers, a program selection system comprising:means at alocation remote from the subscriber location for transmitting thesubscription program signals with an associated signal indentifying theprogram signal as containing subscription program material in at leastone of a plurality of subscriber accessible categories of subscriptionprogram material; means at the subscriber location for receiving thesubscription signals and the associated category identifying signal;subscriber-actuated means at the subscriber location for selecting atleast one category of subscription program material and producing alocal category signal identifying said selected category of subscriptionprogram material; means for comparing said local category signal andsaid received category identifying signal to produce a control signalfor limiting selection of program material to said at least one categoryidentified by said local category signal.
 2. The system of claim 1wherein each subscription program signal contains a scrambled videoportion and is transmitted with an identifying signal unique to programmaterial in said video portion and including means for unscrambling thevideo portion of the received subscription program signal in response tosaid control signal.
 3. The system of claim 1 wherein said associatedcategory indentifying signal is an identifying number unique to theprogram material in the program signal and wherein said comparing meanscomprises means for comparing said local category signal and saididentifying number and producing the control signal in response to saidnumber being within a range of numbers associated with said localcaregory signal.
 4. In a television system in which program signalscontaining subscription program material, and associated signalsidentifying the program signals as containing at least one of aplurality of categories of subscription program material, aretransmitted so as to be available to all subscribers, apparatus at eachsubscriber location for restrictive access to the subscription programmaterial comprising:means for receiving a program signal and anassociated category identifying signal and detecting the associatedcategory identifying signal; means for selecting at least one of saidplurality of categories of subscription program material; means foridentifying the at least one of the plurality of categories ofsubscription program material in the received program signal in responseto the detected category identifying signal; and, means responsive tosaid identifying means for restricting access to the selected categoryof subscription program material in the received program signal.
 5. Theapparatus of claim 4 wherein said identifying means comprises:means forgenerating a local category signal identifying the selected one of theplurality of categories of subscription program material; and, means forcomparing the detected category identifying signal and the localcategory signal.
 6. The apparatus of claim 4 wherein said receivedprogram signal includes a scrambled video portion and wherein saidaccess restricting means comprises means for unscrambling said videoportion and enabling display thereof in response to the identificationof the selected one of the plurality of categories by said identifyingmeans.
 7. A method for program selection in a television system in whichsubscription program signals containing subscription program materialare transmitted to subscribers with associated category signals eachidentifying an associated program signal as containing subscriptionprogram material in at least one of a plurality of categories ofsubscription program material, the method comprising the stepsof:receiving a subscription program signal and an associated categoryidentifying signal; selecting at least one category of subscriptionprogram material at the subscriber location; producing at the subscriberlocation a local category signal identifying the selected category ofsubscription program material; and comparing the local category signaland the received category identifying signal to produce a control signalfor limiting subscriber selection of program material to said at leastone category identified by said local category signal.
 8. The method ofclaim 7 wherein the program signal is scrambled and including the stepofenabling the unscrambling of the program signal in response to thecontrol signal.
 9. The method of claim 7 wherein the local categorysignal is produced by manually setting a control at the subscriberlocation to one of a plurality of positions related to differentcategories of program material.